The Norwegian Freedom of Information Act contains a provision whereby information concerning matters of national security may be excepted from public access. The authority issuing such a document indicates that it is to be excepted from public access by classifying the document with a security grading. The classifications that may be used for national security matters, described in the Norwegian Security Act, range from Restricted to Top Secret.

Only the entity that classified the document, i.e. assigned the initial security grading, may lift or downgrade its classification. Pursuant to the Security Instructions, the Norwegian national security regulations of March 17, 1972, such security classifications are automatically lifted after 30 years, unless it has been explicitly determined that the security grading is necessary for a longer period of time. It is important to be aware that a document may contain information that is confidential pursuant to the ordinary confidentiality provisions of the Norwegian Public Administration Act even when classification according to the Security Instructions expires, and hence nevertheless excepted from public access.